The drug discovery and development process that ultimately brings new drugs to market is a complex and costly process. Traditionally, the early stages of drug discovery utilized affinity binding assays that generally were done in vitro and provided limited information on the ability of a potential drug compound to illicit the effect on the target of interest. Many of these potential leads fail when tested either in cell-based assays or animal model-based validation assays at the preclinical/clinical trials, resulting in high attrition rates. More recently, innovative cell-based technologies including high-content screening technologies have gained popularity in the pharmaceutical and biotech industries. These assay technologies provide functional, kinetic cell-based information on the cellular consequences of target-compound interaction. The data obtained include information on signal transduction pathways, drug mechanisms of action, efficacy, selectivity and cytotoxicity. Most of the existing cell-based technologies that require the use of fluorescent labels or luminescence labels for imaging-based detection are generally focused on evaluating discrete intracellular events (e.g., Ca2+ flux, cAMP generation and accumulation, target translocation, reporter gene generation, etc). Because of the complexity of cell function, cellular responses generally result from integration of multitude signals, and thus assay technologies based on a given single-cellular response or signal tend to fail to generate information regarding the overall integrated cellular response to drug stimulation. The use of labels or the use of artificial enhancements (e.g., transfection or RNAi knockout) or the use of a report gene system, for example, could contribute in an adverse way to elucidating the real cellular physiology of the target of interest. For these reasons, there is a continuing need for being able to assay the effect of molecules on living cells, such as assaying whether the molecule effects a particular signaling pathway, such as a G protein coupled receptor (GPCR) or epidermal growth factor receptor (EGFR), or whether the molecule causes the cell to proliferate or causes the cell to die or stop growing. The use of label free or label independent detection (LID) biosensors is desirable because the biosensors bypass the need for often complex labeling strategies and detection mechanisms. Label free biosensors are more convenient for high through put methods. Disclosed are methods and systems for using label free biosensors to perform any type of cell assay, including assaying signal transduction pathways and cell proliferation and death.